Method for welding longitudinal lobes or fins to tubes



' United States Patent inventors Pembroke 0. Leach;

William P. Jackson; Vernon W. Camp, Chattanooga, Tennessee Appl. No. 852,956

Filed May 19,1969

Patented Dec. 8, 1970 Assignee Combustion Engineering, inc.

Windsor, Connecticut a corporation of Delaware METHOD FOR WELDING LONGITUDINAL LOBES OR FINS TO TUBES 1 Claim, 4 Drawing Figs.

US. Cl 219/137 Int. Cl. B23k 9/00 Field ofSearch 219/137, 125,73, 124; 29/490, 491, 498; 228/50 References Cited UNITED STATES PATENTS 3/1931 Riihr 219/137 2,107,435 2/1938 Birmingham 219/137 2,719,210 9/1955 Chapman 219/137 3,045,340 7/1962 Kolling 219/137 3,059,099 10/1962 Carpenter et al. 219/137 3,127,503 3/1964 Garner et a1 219/124 3,221,135 11/1965 Maier,Jr. 219/137 3,233,074 2/1966 Smith 219/137 3,252,511 5/1966 Gerber 219/137 3,342,973 9/1967 Smith 219/124 Primary Examiner-J. V. Truhe Assistant Examiner-George A. Montanye Attorneys-Carlton F. Bryant. Eldon H. Luther, Robert L. Olson, John F. Carney, Richard H. Berneike, Edward L. Kochey, Jr. and Lawrence P. Kessler ABSTRACT: Welding method for forming longitudinal fins or lobes on tubes by continuously moving a tube and a slightly spaced cylindrical rod, or bar of other cross-sectional geometry, past stationary consumable welding electrodes, which deposit molten metal between the tube and rod, thereby fusing these two members together.

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WILLIAM JACKSON BY VERNON LAMP Wi w A'r-romvsy METHOD FOR WELDING LONGITUDINAL LOBES OR F INS TO TUBES BACKGROUND OF THE INVENTION This is a divisional application of Ser. No. 633,603, filed by Pembroke O. Leach et al on Apr. 25, I967, now abandoned, for Apparatus for Welding Longitudinal Lobes or Fins to Tubes.

Tubes with longitudinal fins thereon are used quite extensively today, particularly in the boiler field. It is common practice to line the furnace walls of steam generators with panels made of tubes and fins welded together. Considerable use is also made of individual tubes which have increased heating surface thereon in the form of longitudinal fins. One present method of forming longitudinal fins on tubes is by use of a consumable electrode which deposits molten metal adjacent to a tube, which molten metal when solidified, forms a fin. This method of welding presents problems, because of difficulty in forming a fin of smooth and even contour, and because of the drastic deformation as a result of the asymmetric and high heat input when only one fin is formed on a tube in this manner.

SUMMARY OF THE INVENTION The present invention is directed to apparatus for forming a longitudinal fin or lobe on a tube by moving a tube and a spaced cylindrical rod or bar of other cross section past stationary consumable welding electrodes, which deposit molten metal between the tube and rod, thereby forming an imperforate web therebetween. The cylindrical rod or bar of other cross section is of such dimension and the welding heat is so controlled that the rod or bar is only partially fused or melted by the electrode, and thus the finished fin has a smooth, uniform, controlled outer extremity along its entire length.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view ofa tube welder embodying the invention;

FIG. 2 is an enlarged view taken on lines 22 of FIG. 1; FIG. 3 is a top view taken on lines 3--3 of FIG. 2; and FIG. 4 is a view showing the finished welded tube and fin.

DESCRIPTION OF THE PREFERRED EMBODIMENT Looking now to FIG. 1, l designates a welding machine. Numeral l2 designates a tube to which, in this application, a cylindrical rod 14 (best seen in FIG. 2) is to be welded. Tube '32 is fed into the welding machine by means of entrance drive rollers 16 and 18, which can be suitably gear or chain driven by means of a motor (not shown). The tubes are held in engagement with the drive rollers by means of upper entrance guide rollers 20 and 22. The cylindrical bar 14 is driven through the welding machine by drive roller 19, and is held in engagement therewith by roller 23.

The filler wire 24, which will form a portion of the web between tube 12 and bar 14, is fed into the welding machine by means of filler wire guide 26. Electrode wire 28 is positioned above the filler wire 26 by guide 30. The electrode wire 28, filler wire 24, tube 12 and bar 14 are electrically connected such that an arc is established between the consumable electrode 28, filler wire 24, bar 14, and the tube 12. In order to shield the weld to prevent oxidation thereof and to protect the backup shoe 40, a flux dispensing means 34 directs protective material around the weld area. Suitable flux recovery means 36 picks up any excess flux. Air chisel 38 clears or removes the slag from the weld.

A plurality of feed in racks 60 support the tubes on the entrance end of the welding machine. Likewise, a plurality of feed out racks support the tubes at the outlet end.

A backup shoe 40 is positioned beneath the welding head, and the upper surface thereof supports the molten metal during the welding operation. The backup shoe is made ofcopper, or other suitable material, and acts as a chill bar for tube 12 and bar 14 as they move past the welding head is shown. Backup shoe 40 has guide member 70 integral therewith, which accurately positions the bar 14 immediately adjacent to the ridge 74, so that it will form the outer extremity of the fin after the welding operation has been completed.

FIG. 4 shows the finished finned tube, after the welding operation has been completed. The cross hatching indicates the portion of the metal which was fused, or was molten during the welding. As can be seen, the arc struck by consumable electrode 28 completely melts filler wire 24. Also, a controlled portion of rod 14 is fused, as is some of the wall of tube 12. The portion of rod 14, indicated at 82 in FIG. 4, does not become fused, and thus a continuous, uniform, rounded edge is formed on the outer extremity of the finned tube.

This type of formation of fins on tubes results in a number of advantages. Fins of a greater width can be made than is possible by other present-day methods. The outer edge of the fin has a desirable smooth, uniform surface along its entire length. Because of the symmetric heat input between tube and bar, and because the ba is never fully molten, a finned tube straight enough for further processing without straightening may be produced.

Although specific apparatus has been described, it should be understood that the welding apparatus of the invention has utility in refinements other than that herein employed to illustrate and explain the same. For example, it should be obvious that by utilizing a welding head and cylindrical bar on the other side of the tube, it would be possible to form fins on both sides of a tube simultaneously. Also, the extremity of the fin or lobe so formed can be any desired shape, such as a lap joint or weld groove, etc. We therefore do not wish to be limited in the scope of our invention except as may be required by the claims.

We claim:

I. The method of forming a longitudinal fin on a tube including the steps of moving a tube past a welding station, also moving a solid rod which is parallel to and spaced a given distance from the tube past the welding station, depositing molten metal between the tube and rod as they move past the welding station, said molten metal completely bridging the gap between the rod and tube, the original distance between the tube and rod being such that a major portion of the finished fin is made up of fused metal, the amount of molten metal deposited between the tube and rod being insufficient to completely melt the rod, so that the finished fin has a smooth, outer extremity. 

